This invention relates to transport of signals of different protocols.
With the increase in communication traffic, networks are being demanded to be faster and larger in capacity. Large-capacity transport owing to data multiplexing has come to be used in backbone communication networks that connect line concentrators, bases, or providers' networks to each other. Examples of this large-capacity transport include Synchronous Digital Hierarchy/Synchronous Optical Network (SDH/SONET) in which low-rate signals are multiplexed into a signal of a predetermined rate to be transported as the signal, and Optical Transport Network (OTN) which accomplishes large-capacity transport by employing the concept of an optical path that is suitable for wavelength division multiplexing (WDM).
A problem of the large-capacity transport network technologies described above is that accommodating a plurality of signals makes the apparatus configuration large. In this situation, for example, in JP 2003-143097 A, there is disclosed a technology in which the detection of synchronization among a plurality of frame rates in SDH or SONET is accomplished with a single circuit. In JP 2008-227995 A, there is disclosed a multi-rate interface board in which low-rate signals that are not standardized by OTN frame standards are turned into an OTN frame irrespective of the signal type.
In recent years, the diversification of signals (protocols) coupled to a network, which reflects their different uses, has also been observed. The link layer, for instance, has a mixture of various protocols such as the Ethernet (trademark), Fibre Channel, and InfiniBand.
Against this background, there is an increasing demand in the field of networks where links having different transport data rates are multiplexed before transmitted for a signal multiplexing technology compatible with multiple rates which does not depend on a specific protocol or a specific transport data rate.
The technology disclosed in JP 2003-143097 A detects, on the premise that transported signals are in the formats of SDH and SONET which are networks using synchronization protocols that heavily rely on accurate and stable clocks, multiple rates by detecting synchronization detection patterns unique to the respective formats. This technology therefore cannot detect signals of, for example, the Ethernet which runs on asynchronous clocks.
While transport in the OTN format allows for mapping irrespective of the signal type, as well as integrated monitoring control of the overall network, implementing the technology requires putting in a plurality of transport apparatus in order to cover each OTN frame type standardized by the ITU in advance.
The technology disclosed in JP 2008-227995 A detects multiple rates with the use of an optical module code which is identification information indicating the type of an optical module. This technology is therefore not applicable to apparatus in which an optical module is not installed.